Design of CLARI: A miniature modular origami passive shape-morphing robot

Miniature robots provide unprecedented access to confined environments and show promising potential for novel applications such as search-and-rescue and high-value asset inspection. The capability of body deformation further enhances the reachability of these small robots in complex cluttered terrains similar to those of insects and soft arthropods. Motivated by this concept, we present CLARI, an insect-scale 2.59g quadrupedal robot capable of body deformation with tethered electrical connections for power and control and manufactured using laminate fabrication and assembled using origami pop-up techniques. In order to enable locomotion in multiple shape configurations, we designed a novel body architecture comprising of modular, actuated leg mechanisms. Overall, CLARI has eight independently actuated degrees of freedom (two per modular leg unit) driven by custom piezoelectric actuators, making it mechanically dextrous. We characterize open-loop robot locomotion at multiple stride frequencies (1-10Hz) using multiple gaits (trot, walk, etc.) in three different fixed body shapes (long, symmetric, wide) and illustrate the robot's capabilities. Finally, we demonstrate preliminary results of CLARI locomoting with a compliant body in open terrain and through a laterally constrained gap, a novel capability for legged robots. Our results represent the first step towards achieving effective cluttered terrain navigation with adaptable compliant robots in real-world environments

Geometric Mechanics of Contact-Switching Systems

Discrete and periodic contact switching is a key characteristic of steady state legged locomotion. This paper introduces a framework for modeling and analyzing this contact-switching behavior through the framework of geometric mechanics on a toy robot model that can make continuous limb swings and discrete contact switches. The kinematics of this model forms a hybrid shape space and by extending the generalized Stokes' theorem to compute discrete curvature functions called stratified panels, we determine average locomotion generated by gaits spanning multiple contact modes. Using this tool, we also demonstrate the ability to optimize gaits based on system's locomotion constraints and perform gait reduction on a complex gait spanning multiple contact modes to highlight the scalability to multilegged systems.Comment: 6 pages, 7 figures, and link to associated video: https://drive.google.com/file/d/12Sgl0R1oDLDWRrqlwwAt3JR2Gc3rEB4T/view?usp=sharin

Femtosecond laser fabricated nitinol living hinges for millimeter-sized robots

Nitinol is a smart material that can be used as an actuator, a sensor, or a structural element, and has the potential to significantly enhance the capabilities of microrobots. Femtosecond laser technology can be used to process nitinol while avoiding heat-affected zones (HAZ), thus retaining superelastic properties. In this work, we manufacture living hinges of arbitrary cross-sections from nitinol using a femtosecond laser micromachining process. We first determined the laser cutting parameters, 4.1 Jcm^-2 fluence with 5 passes for 5 um ablation, by varying laser power level and number of passes. Next, we modeled the hinges using an analytical model as well as creating an Abaqus finite element method, and showed the accuracy of the models by comparing them to the torque produced by eight different hinges, four with a rectangular cross-section and four with an arc cross-section. Finally, we manufactured three prototype miniature devices to illustrate the usefulness of these nitinol hinges: a sample spherical 5-bar mechanism, a sarrus linkage, and a piezoelectric actuated robotic wing mechanism.Comment: 6 pages, 6 figures, submitted to IEEE RA-

A Population-Level Analysis of Neural Dynamics in Robust Legged Robots

Recurrent neural network-based reinforcement learning systems are capable of complex motor control tasks such as locomotion and manipulation, however, much of their underlying mechanisms still remain difficult to interpret. Our aim is to leverage computational neuroscience methodologies to understanding the population-level activity of robust robot locomotion controllers. Our investigation begins by analyzing topological structure, discovering that fragile controllers have a higher number of fixed points with unstable directions, resulting in poorer balance when instructed to stand in place. Next, we analyze the forced response of the system by applying targeted neural perturbations along directions of dominant population-level activity. We find evidence that recurrent state dynamics are structured and low-dimensional during walking, which aligns with primate studies. Additionally, when recurrent states are perturbed to zero, fragile agents continue to walk, which is indicative of a stronger reliance on sensory input and weaker recurrence

Scaling down an insect-size microrobot, HAMR-VI into HAMR-Jr

Here we present HAMR-Jr, a \SI{22.5}{\milli\meter}, \SI{320}{\milli\gram} quadrupedal microrobot. With eight independently actuated degrees of freedom, HAMR-Jr is, to our knowledge, the most mechanically dexterous legged robot at its scale and is capable of high-speed locomotion (\SI{13.91}{bodylengths~\second^{-1}}) at a variety of stride frequencies (\SI{1}{}-\SI{200}{\hertz}) using multiple gaits. We achieved this using a design and fabrication process that is flexible, allowing scaling with minimum changes to our workflow. We further characterized HAMR-Jr's open-loop locomotion and compared it with the larger scale HAMR-VI microrobot to demonstrate the effectiveness of scaling laws in predicting running performance.Comment: IEEE International Conference on Robotics and Automation 2020 (accepted

Fabrication of Paper-Templated Structures of Noble Metals

This manuscript describes a simple and rapid method for fabricating freestanding structures composed primarily (>94% w/w, and 55–80 at%) of noble metals (e.g., gold, silver, platinum, etc.) and having physical morphologies that resemble paper, thread, or fabric. In this method, templates (i.e., pieces of paper, or cotton fabric) are loaded with aqueous solutions of salts of noble metals, and then the cellulosic component is burned off in a furnace held at high temperatures (i.e., from 550 °C to 800 °C, depending on the procedure, in air). Even though the environment in a furnace is ostensibly oxidizing (e.g., hot air), the metal ions are reduced to elemental metal and form paper-template or fabric-templated structures that have morphologies similar to that of the material from which they were derived (i.e., paper or fabric). Paper template structures are fibrous, permeable to gases and liquids, electrically conductive, and in some cases (e.g., paper templated gold and paper template platinum structures), their surfaces are electroactive. The surface areas of paper-templated structures are more than 20 times higher than their projected areas. Paper-templated structures thus have properties that make them potentially useful in catalysis, sensing, and electroanalysis.Chemistry and Chemical Biolog

Exploring the association between Alzheimer’s disease, oral health, microbial endocrinology and nutrition

Longitudinal monitoring of patients suggests a causal link between chronic periodontitis and the development of Alzheimer’s disease (AD). However, the explanation of how periodontitis can lead to dementia remains unclear. A working hypothesis links extrinsic inflammation as a secondary cause of AD. This hypothesis suggests a compromised oral hygiene leads to a dysbiotic oral microbiome whereby Porphyromonas gingivalis, a keystone periodontal pathogen, with its companion species, orchestrates immune subversion in the host. Brushing and chewing on teeth supported by already injured soft tissues leads to bacteraemias. As a result, a persistent systemic inflammatory response develops to periodontal pathogens. The pathogens, and the host’s inflammatory response, subsequently lead to the initiation and progression of multiple metabolic and inflammatory co-morbidities, including AD. Insufficient levels of essential micronutrients can lead to microbial dysbiosis through the growth of periodontal pathogens such as demonstrated for P. gingivalis under low hemin bioavailability. An individual’s diet also defines the consortium of microbial communities that take up residency in the oral and gastrointestinal (GI) tract microbiomes. Their imbalance can lead to behavioural changes. For example, probiotics enriched in Lactobacillus genus of bacteria, when ingested, exert some anti-inflammatory influence through common host/bacterial neurochemicals, both locally, and through sensory signalling back to the brain. Early life dietary behaviours may cause an imbalance in the host/microbial endocrinology through a dietary intake incompatible with a healthy GI tract microbiome later in life. This imbalance in host/microbial endocrinology may have a lasting impact on mental health. This observation opens up an opportunity to explore the mechanisms, which may underlie the previously detected relationship between diet, oral/GI microbial communities, to anxiety, cognition and sleep patterns. This review suggests healthy diet based interventions that together with improved life style/behavioural changes may reduce and/or delay the incidence of AD

Robustness of Biological and Bio-inspired Exoskeletons

The single greatest difference between biological organisms and human technologies today is perhaps robustness. Robustness is broadly defined as a system's ability to maintain performance despite disturbances. Qualitatively, a complex system may be called robust if it exhibits some or all of the following properties - multi-functionality, fault tolerance, damage resistance, modularity and redundancy. However, even the best engineering approaches that have attempted to consider some of these aspects find themselves 'fragile', slow and computationally intensive. On the other hand, I contend that biological systems are truly robust and capable of a plethora of complex activities such as locomotion, reproduction, respiration etc. In addition, animals constantly overcome challenges of growth and perform self-repair and learning, still a challenge for even the best engineered systems today. Using the cockroach as my model organism, I have investigated the role of exoskeletons in enabling robust high-speed locomotor behavior in cockroaches. Specifically, I have discovered that the cockroach exoskeleton (1) is effective at dealing with external loads/impulses through body reconfiguration,(2) facilitates (or enhances) rapid horizontal to vertical transitions during high-speed running, and(3) compensates for damage (loss of appendages (or its parts)) undergoing a limited decrement in high-speed running performance.Based on the impressive locomotion performance by cockroaches despite perturbations, internal and external to the animals, we propose that robustness is a crucial measure of the effectiveness of a system's performance